The invention relates to a perforated cover for holes and vents which pass air or liquid and which pass air or liquid and which can modify existing covers, i.e., as to the size and shape of the apertures in the cover. Most prior art covers have been made of metal and especially prior art sewer drain covers for use on public streets. These prior art covers were usually made of cast iron and set into metal frames embedded in the concrete. They were made heavy to prevent theft and early models had large slots generally parallel with the street. These slots have caused accidents to bicycles and the riders. The wheels of the bicycle being abruptly caught in the slot and throwing the cycler. This cover will change the configuration of the existing cover to prevent the wheels of the cycle from dropping into the slots and yet retain all the strength of the original cover. The polymers from which the covers are made are strong, yet lightweight. Prior metal covers for many drains or vent can be covered or totally replaced by this cover.